This invention relates to an improvement in a sewing machine controller and more particularly to a sewing machine controller for computing work efficiency to sew a piece of cloth and determining whether or not the work efficiency or sewing is good, thereby improving the productivity of sewing.
A conventional sewing machine controller will be discussed with reference to FIG. 6. In the figure, a sewing machine 1 comprises a sewing machine mechanism section 9 containing a mechanism for forming seams on cloth 7 with a sewing machine needle 5 on the top of a sewing machine table 3, a sewing machine motor 11 for driving the sewing machine mechanism section 9, a cloth press section 13 for pressing and holding the cloth 7, a thread cutting mechanism 15 for cutting thread with which the cloth 7 is sewed, a pedal 19 having a signal generation section 17 for generating a thread cutting command given to the thread cutting mechanism 15 and turning and speed commands of the sewing machine motor 11, a sewing machine needle detector 21 for detecting the position of the sewing machine needle 5, thereby counting the number of sewing times of the sewing machine needle 5, and a controller 23 being disposed in a wing of the sewing machine table 3 for controlling the operation of the components.
The controller 23 comprises an operation command section 25 for generating sewing machine operation commands based on a signal of the depressing amount of the pedal 19 input from the signal generation section 17, a sewing machine needle 5 position detection signal input from the sewing machine needle detector 21, etc., a motor drive section 27 for driving the sewing machine motor 11 in response to output of the operation command section 25, a thread cutting drive section 29 consisting of a solenoid, etc., for driving the thread cutting mechanism 15 in response to output of the operation command section 25, a motor operation time counter 31 for integrating the on time of output of the motor drive section 27, a sewing machine operation time counter 33 for integrating the on time of an operation switch 23a of the controller 23, namely, the operation time of the controller 23, and a display section 35 for displaying both the motor operation time counter 31 and the sewing machine operation time counter 33 on a liquid crystal display, etc., through the operation command section 25.
The operation for sewing cloth 7 with the sewing machine configured as described above will be discussed with reference to FIG. 6. First, a worker places cloth 7 on the table 3 and presses and holds the cloth 7 under the cloth press section 13. The worker turns on the operation switch 23a of the controller 23. When the off-to-on transition of the signal is made, the sewing machine operation time counter 33 counts the on time of the controller 23 and the time is displayed on the display section 35 through the operation command section 25. The controller 23 is turned on only when the sewing machine 1 is operated, and is turned off when the sewing machine 1 stops. Thus, the integral of the operation time of the controller 23 is assumed to be the operation time of the sewing machine 1.
Next, to start sewing, the worker depresses the pedal 19. A signal is input through the signal generation section 17 to the operation command section 25 in response to the depressing amount of the pedal 19. The operation command section 25 turns the sewing machine motor 11 through the motor drive section 27 at the rotation speed responsive to the depressing amount of the pedal 19. The sewing machine motor 9 operates the needle 5 through the sewing machine mechanism section 9 for sewing the cloth 7. On the other hand, the motor operation time counter 31 counts the time during which the motor drive section 27 generates a motor turning command, and the count is displayed on the display section 35 through the operation command section 25.
At the termination of sewing the cloth 7, the worker takes his or her foot off the pedal 19. A stop signal is input from the pedal 19 through the signal generation section 17 to the operation command section 25, which then stops generating the motor operation command given to the motor drive section 27. In response to the stop signal, the motor operation time counter 31 stops counting and the count Ta is displayed on the display section 35.
Next, the worker kicks the pedal 19. A kick signal from the pedal 19 is input through the signal generation section 17 to the operation command section 25, which then gives a thread cutting signal to the thread cutting drive section 29 for operating the thread cutting mechanism 15 for cutting the thread.
Upon completion of a predetermined number of pieces of cloth 7 by repeating the operation of the sewing machine as described above, the worker turns off the power switch 23a. The sewing machine operation time counter 33 stops counting and the count To is displayed on the display section 35 through the operation command section 25.
Next, the work efficiency of the cloth 7 is determined by the actual work time and the stop time per piece of the cloth 7. First, the actual work time is found by dividing the integral value Ta of the motor operation time displayed on the display section 35 by the number of sewed pieces of cloth with a calculator, etc.
The stop time is assumed to be the stop time of the sewing machine 11. From the count To of the sewing machine operation time counter 33, the integral value Ta of the motor operation time, and the number of sewed pieces of cloth, n, the stop time per piece of cloth, tr=(To-Ta)/(n-1) is found. The finished cloth 7 is visually checked as quality inspection before shipment.
However, the conventional sewing machine controller involves a problem of improper grasping of work efficiency. First, the actual work time per piece is found from the operation time of the sewing machine 1 and the number of sewed pieces, but accurately the time to finishing of cloth 7 is not only the operation time of the sewing machine motor 11. That is, to finish cloth 7, the sewing direction is changed and the thread is cut after the sewing machine motor 11 is stopped; the time is also contained in the above-mentioned actual work time.
Second, since the total actual work time to finishing of one sewing product is found, the found time is not related to the form, sewing pattern, etc., of cloth 7. Thus, if the work time is determined to be long, which sewing part is the cause of prolonging the actual work time is not made clear; it is difficult to remove the cause for shortening the work time.
Third, since quality inspection is executed for weeding out defective items after cloth 7 is finished, the quality inspection step is also contained in the time to finishing of cloth 7; resultantly, the inspection step lowers the total work efficiency.
Fourth, for the worker to adjust the depressing amount of the pedal 19 of the sewing machine with his or her foot, it is empirically known that the worker needs also take care of his or her foot, lowering the work efficiency; the countermeasure is insufficient.